As one of the major aids used by the bare-handed diver when diving, the snorkel is designed to help the diver keep continued breathing while floating in the water to search for watching the underwater scene.
The most widespread snorkel is a simple J-shaped hollow pipe made of rubber or plastic, about 30-35 cm long with a caliber of about 1.5-2.0 cm. When to use it, the snorkel is installed at the front end of rubber tape on one side of diving mask, the mouth at the top end of snorkel is open, and the bent part at the lower end thereof is held in the diver's mouth so that he or she can breathe with his or her mouth. When folating up, the said mouth at the top end of snorkel is about 10 cm above the water level, the diver can watch the underwater scene on the one hand and keep continued breathing through the snorkel on the other hand. However, when diving down, the snorkel will sink together with the diver, the water will naturally enter into the snorkel through the said mouth at the top end thereof, so the diver has to close his or her mouth tightly and he or she will not swallow the water in the snorkel. When floating up, the diver has to drain the water in the snorkel in order to be able to breathe continuously, such an action is called "blowing snorkel" which denotes that the diver forcefully jets out the air in his or her abdomen through his or her mouth and the water in the snorkel is then frained from the mouth at the top end thereof through the air pressure, so the diver can breathe continuously. What is mentioned above indicates the structure and usage of snorkel in general.
The foregoing conventional snorkel during use has the following drawbacks:
(1) When floating up after diving down, the diver is always in urgent need of breathing the air in quantities as soon as possible but he or she has to perform "blowing snorkel" forcefully so as to be able to breathe through draining the water in the snorkel, his or her difficulty is imaginable. Therefore, the diver is always hurrying up to pull out the said bent part at the lower end of snorkel from his or her mouth (such an action is the so-called "pulling snorkel") but omitting the action of "blowing snorkel" so as to float up to breathe with his or her mouth at once (The divers in general urgently need oxygen in quantities when they float up since they feel suffocated for a long time during diving down, it is not enough for them to only breathe with nose). If the water in the snorkel is not well drained through "blowing snorkel", the diver swallowed the said water to cause choking the bronchia with water (Most of the drowned are suffocated to death because of choking the bronchia with water--a phenomenon of water accumulated in the lungs, and such a choking in 1-2 minutes will lead to death).
(2) Since the water in the snorkel cannot be entirely drained, a little bit of such water will accumulate in the bottom at the lower end of snorkel (namely, the bent part thereof), and when the diver uses it once again, the passage. of breathing air flow will generate an odd noise, he or she feel suffering something like pneumonia and asthma, it has to drain the accumulated water as a whole in the snorkel and then the snorkel may be usable, but it is very inconvenient for such a disposal in the water.
(3) So far as the conventional snorkel is concerned, the mouth at the top end thereof is only about 10-15 cm above the water level when the diver is floating, and no water check device is provided to the mouth at the tail end of snorkel, the tail end directly communicates with the diver's mouth, so a trifling carelessness (such as the snorkel is inclined) or a wave on the water surface may cause the water flowing into the snorkel from time to time to be inhaled into the diver's mouth and lead to the danger of swallowing water or choking the bronchia with water.
(4) The inhaling and exhaling passages of conventional snorkel during use are the same one passage, namely, the inhalation and exhalation are continuously alternated on one passage in a single tube, so when inhaling, the fresh air above the water level is inhaled into the diver's lungs through the tube; and when exhaling, the waste carbon dioxide in his or her lungs is exhaled out of his or her body through the same one tube. However, after exhaling, the interior of tube is filled with the exhaled waste carbon dioxide, so when inhaling once again, the diver has to inhale the waste carbon dioxide filled in the snorkel first and then can inhale the fresh air required by him or her from the exterior of said snorkel, and the residual carbon dioxide in the snorkel is about 1/4 to 1/3 quantity of air inhaled into the human body each time, namely, when inhaling each time, the diver has to inhale the waste carbon dioxide amounting to 1/4 to 1/3 quantity of air approximately. Therefore, while using the snorkel for a long time, the diver will suffer bodily discomfort, gasp and headache because the required fresh air is not enough but the waste carbon dioxide is too much. Such symptoms denote the anoxia and carbon dioxide poisoning which form a considerable damage to the diver's body and consume and waste his or her physical strength very much.
What are mentioned above show the major drawbacks of conventional snorkel which leaves much to be desired and is not a bare-handed diving aid to be used by everyone without getting through the required training and practice or guidance.